Process for producing color prints and products



March y19, 1946. L.. s. TRIMBLE 2,396,726

PROCESS FOR PRODUCING COLOR PRINTS AND PRODUCTS Filed Feb. 25, 1942 256020 /YEGA T/ VE' W CEL/ ULO/D I Bnveutor, WYE 5 7b/M5LE E M )MM (Ittorneg Patented te, 194e PROCESS FOR PRODUCING COLOR PRITS AND PRODUCTS Lyne S. Trimble, North Hollywood, Calif. application February 2s, 1942, serieu No. 431,999 4 '7 Stalins. My invention relates `in general to the art of color photography with particular reference to new and novel methods for producing combinations of photographic images and separately coloring them to produce color` positive films suitable foruse in motion pictures. While the process of my invention is applicableto both still and motion picture photography, it nds its widest range of application in the latter branch of the art, and consequently I will conne my description of a preferred form of my invention to its adaptation in motion picture transparencies, it being understood that whenever the term nlm is used, it

is meant to include all types i. ilm, photographic plates, and paper for all branches of photography.

In producing colored Amotion pictures by subtractive methods. one oi.' two types' of film is generally used; first a nlm which comprises a base with a layer of emulsion upon each side thereof, or second, a. nlm comprising a base with a layer of emulsion upon only one side thereof, which said layer may have the same sensitivity throughout or may have a varyingror stratied sensitivity,

depending upon the use to which it is to be put. In producing positive prints in color, by the use of film having an emulsion layer on one side only, it is usual to have the emulsion sensitized substantially uniformly throughout, one photographic color'value image being produced in the upper or outer stratumof the emulsion layer by printing from a negative to the face of the emulsion, and a second photographic image of another color value is printed or produced inthe lower or innerstratum by printing through the base from another color value negative. Ii the process is a two color process, this constitutes the entire printing step, however, if a three colorprocess is being followed various methods may be employedl for producing three images in the emulsion layer.

Imbibition is a common procedure whereby a. re-

' lief image previously saturated ,with dye is placed in contact with the positive iilm whlchreceives the dye in' proportion to the matrix image density' for a given contact time and temperature. Several methods have been utiliued'thatfrender a printed and developed image transparent so that a third image may be printed through this first imager Ii'a double emulsion film, the so-called duplitized positive, is being used two images may be produced on-one side ofthe base and a third image 'on the opposite side.

various color processes have been promulgated which utilize two images in separate strata of a single emulsion and color theimages substantially v complementary colors. I have found, however, Il h de to silver iodide which is not very responsive that it is very diiiicult to control the treatment of two images in separate strata of thesame emulsion layer so as to produce separate colored images which are satisfactory, since in the usual s known processes of this type, the step or steps lwhich are used in coloring -the outer image usually aiect the inner ima/ge to its detriment,or yield an outer image which is subsequently modified or otherwise damaged by the treatment prescribed lo for the inner image. i

An object oi! my invention is to pro'vide a process of color photography whereby ay satisfactory combination of two images in a single emulsion layer may be utilized in combination with a third l5 image.

Another object of my invention is to provide a process whereby'the production o f two images Y in the same strata, as well as their subsequent conversion to substantially com lementary colors,

2o is accomplished in the case o either image as though the other image was not present.

Another object of my invention 'is to provide a process in whichan image may be printed in an emulsion through an image already present in said emulsion without substantially altering its form and as though said rst printed image had not been present.

Another obiect of my invention is to provide a process vof treatinga silver image chemically 3 whereby said silver image is rendered unaffected by a subsequent treating solution normally capable of reacting with said silver image.

In a preferred form of my invention, I produce 2 two images, a yellow color value image and a masenta-color" value image .in the outer strata on i each side of a double coatedtorduplltized illm by simultaneously printing the two images in register from suitable color separation negatives. These images are developed in the usual manner so that v l0 they both comprise free silver. After sumcient wash to remove all traces oi the developing solution the images are chemically sealed in such a manner that a suitablyv proportioned v blue tone capableof converting a silver image into a blue color value image of Prussian blue will have no This is accom-l effect upon the above images.

plished by treating the above silver images with a solution comprising a bichromate oi' an alkali metal, and analkali bromide or chloride. The essential action depends upon the presence of the to subsequent exposure and development. l. The pH of the solution must be adjusted such that the silver image will not be bleached to a silver halide; the exact value will depend upon the temperature, immersion time, and gelatine hardness. In general any pH value above 3.5 is satisfactory, The

' exact natureV of such sealing action is not known. It may be that of gelatine hardening by virtue of chromium oxide formation, or it may be an actual silver grain coating of chromium-oxides or hydroxides. The chemical concentration of the two constituents may be varied considerably depending upon the immersion time, solution tempera' ture, and lm agitation. I have found the best results using a range of 2 to 3 per cent of potassium dichromate and 1 to 2 per cent of potassium bromide coupled with an immersion time of about nine minutes. This treatment is followed by a suitable wash to remove the above solution after which the hlm is dried. Inasmuch as there has been no fixing step and the lm is still light sensitive, .all work must be conducted under suitable safe lights.

The blue color value image Ais printed onto the film in the following manner. First the sound track is printed utilizing an ultra violet filter in the sound printer. 'I'his is customary in black and white work: it has the effect of restricting the image vtothe surface of the stock, hence by virtue ofV restricted dispersion. the image is quite sharp. This track and the blue color value image may be printed on either side of the positive stock, in the preferred form it is printed on the side carrying the yellow. color value image. This blue color value image is now printed from a suitable color separation negative, through` the yellow negative. or a duplicate thereof, having an equal gamma or contrast as the positive yellow image. See li'igure 1. The formerly printed and treated yellow positive I, and the yellow printer 2 which is the blue record negative when combined with the above conditions results in a perfect neutral density throughout the picture area; that is, a mask such vthat the yellow positive image is rendered entirely ineffective. It is then only necessary to increase the printing light intensity sufiiciently to penetrate through this neutral density and print the blue color value image. .'I'he silver images representing the yellow positive and the yellow negative should be of equal gamma .or contrast. The actual grain condition of the treated silver image as well as the exact position of the images on the curves representing the sensitometric characteristics of the negative and positive stocks combine to make a slight deviation from the above condition allowable. It will be understood, however, that a uniform density field is required, and not merelya combination oi.' negative and positive as is often utilized to give a color corrected image. Printing through the combined negative and posi` assenso tions of Figure 1 and that the blue color value image is produced as though the yellow color value image had not been present. This blue color value image and sound track are developed `to suitable contrasts and the film well washed. The result is shown in Figure 2.

The next step in my process is to convert this last developed blue color value image to Prussian blue in a blue toning solution capable of producing complete image conversion without .affecting the two images sealed-by the above mentioned method. A typical formula which completes the image conversion in approximately four minutes is Ferrie ammonium oxalate grams-- 6 Potassium ferricyanide do 6 sulfuric acid ml 1 Water to make liter.- l

This is followed by a wash of about four minutes, then by complete fixation of all silver salts present by a suitable bath of sodium thiosulfate -V images to their respective colors.

. dyes, such as vanadium ferrocyanide, copper tive for color correction purposes results in an image. whereas a print made through the correct combination discussed above'will produce a uniform field oi' exposure Iinst as though the two films had been replaced by a neutral density lter. i

emulsion. A grey base or anti-halatlon negative, l

of course, helps this situation," but I have found ferrocyanide, or silver iodide, or one may be dyed and the other toned. By floating each side ofthe film on the respective basic dye solutions the proper colors are adsorbed upon the mordants. My preferred-form involves basic dye mordantins because of the Wide range of colors available. The silver images are converted to silver iodide in a bleach of the following composition:

Iodine i;xams..l 2 Potassium iodide -s do 50 vSodium acetate dn 5 Acetic acid ml 5 Water to make liter-- 1 In the claims 'I use the term "certain treating solutions to include the use of either a single certain treating solution or a plurality of certain treating solutions.

This is followed by a clearer of 5% of sodium bisultite and a short wash. Standard dyes such as Rhodamine and Auromine are suitable for adsorption upon the silver iodide mordant. Th..`

film is well washed to remove excess dye from the gelatine and dried. The result is a three color positive capable, upon projection, of reproducing the original subject in accurate color rendition.

While I have described one preferred form of my'invention, the principle of printing an image in the described manner has many other useful applications Furthermore, two images may be printed in such a manner on a single emulsion nlm, with subsequent coloring oi these two and the production of a third image by ixnbibition. This of course is applicable to duplitized lm Awhere the imbibed image is placed on the non image bearing emulsion. In another modification two images may be printed, developed, one

`side of the film floated on a solution whereby the the sharpest image is obtained under the condi- (5 image on that side is rendered unaifected by a developing said last printed image andv converting said last printed image to a suitable color by means of said certain treating solutions. and then converting said iirst mentioned images to suitable colors.

3. A process of producing three color positive prints which comprises printing in register from suitable color separation negatives `two color value certain forms'of my invention which I now consider to be the best embodiments thereof, I desire to have it understood that the forms shown are merely illustrative and that the invention is not to be limited t0 the details disclosed herein, but is to b e accorded the full scope of the appended claims.

I claim:

1. A process of producing three color'positive prints which comprises printing in register from suitable color separation negatives two color value images on a transparent support carrying a silver halide emulsion layer on each side, said images being printed on the outer surfaces of said emulsion layers, 'developing said images, treating said images with a solution comprising a bichromate of an alkali metal and a chemical selected from the group consisting of` alkali chlof rides and alkali bromides, the ingredients being in such concentration and the pH value being so .adjusted that said images are not substantially alm tered from metallic silver but said images are ren-. dered unaffected by certain treating solutions nor-l images on a transparent support carrying a silvei halide emulsion layer on each side, said images being printed on the outer surfaces of said emulsion layers, developing said images, treating said images with a solution comprising a, bichromate of an alkali metal and a chemical selected from the group consisting of alkali chlorides and alkali bromides, the ingredients being in such concentration and the pH value being so adjusted that said images-are not lsubstantially altered frommetallic silver, but said images are rendered un aiected by certain treating solutions normally capable of reacting with said images, printing one other colorvalue image on said transparent support already carrying two 'silver images through and in register with one of said first mentioned images and the negative from which said one image was printed, developing said last printmally capable of reacting with said images, printing one other color value image on said transparent support already carrying two silver images through and in register with one of said first mentioned images and the negative from which said one image was printed in such a manner that said other color value image is produced in back of and interpenetrating with said one image out substantially as ii' no other image had been present, developing said lastmentioned image and converting said last mentioned image to a suitable color by means of said certain treating solutions, and then converting said rst mentioned images to suitable colors. c

2. 'A process of producing three color positive prints which comprises printing in register from suitable color separation negatives two color value images on a transparent support carrying a silver halide emulsion layer on each side, said images being printed on the outer surfaces of said emulsion layers, developing said imagestreating said images with a solution comprising a bichromate of an alkali metal and a chemical selected from the group consisting of alkali chlorides and alkali bromides, the ingredients being in such concentration and the pH value being so adjusted that 40 fected by certain treating solutions normally caed image and converting said last printed image to a suitable color by means of said certain treating solutions, and the converting said :first mentioned images to suitable colors.

4. A processy of producing colorl positive prints which comprises printing at least one color value image from a suitable color separation negative on a silver halide emulsion layer on a transparent support, said image being printed on the outer surface of said emulsion layer, developing said image, chemically treating said image in such a manner that said image is not substantially a1'- tered from metallic silver, but is rendered unafpable of reacting with said silver image, printing one other color value image on said emulsion layer capable of reacting with said images, printing one other color value image on said transparent sup port already carrying two silver images through and in register with one of said first mentioned images and the negative from which said one image was printed in such manner that the negative to be printed is in between the positive and the negative from which said one image was printed and which negative to be printed has its emulsion adjacent to the emulsion oi the positive,

already carrying at least one silver image through said first mentioned image and the negative from which said rst mentioned image was printed in such a manne;` that the negative to be printed is in between the positive and the negative from which said one image was printed, developing and converting said last mentioned image to a suitable color by means of said certain treating solutions and converting said iirst mentioned image to a suitable color. y

5. A process of producing color positive prints whichV comprises printing from suitable color sep aration negatives `two color value images on a transparent support carrying a silver halide emulare not substantially' altered from metallic silver but are rendered unaffected by certain treating solutions normally capable of reacting with said silver images, printing one other color value image on said transparent support already carrying two silver images through and in register with one of saidflrst mentioned images and the negative from which said one image was printed in such a manner that said negative to be printed is in between the positiveand the negative from which said one imagewas printed and which negative to be printed has its emulsion adjacent to the emulsion of the positive, developing said last mentioned image, converting said last mentioned image by means of said certain treating solutionsto a Prussian blue 4. s :,soam

through and in register with said one of said first l0 mentioned images and the negative from which said one image was printed in such a manner that thenegative to be printed is in between the positive andthe negative from which said one image was printed and which negative to bev printed has i5 its emulsion adjacent to the emulsion o! the positive.

7. In a process of producing color positive prints. the step of treating at least one color value silver image with a non-bleaching solution comprising from approximately two to approximately A .three percent o! a bichromate of an alkali metal and from approximately one to approximately two percent of a chemical selected from the group consisting of alkalibromides and alkali chlorides.l the pH value of said solution being above 3.5 and the time of treatment being oi the order of nine minutes so that said image is not substantially altered from metallic silver but said image is ren-- dered unaffected by certain treating solutions normally capable of reacting with said image.

LYNE S. TRIMBLE. 

